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Area forecast discussion
National Weather Service Grand Rapids Michigan
327 am EDT sun Sep 15 2019

Latest update...
synopsis/discussion/marine

Synopsis...
issued at 310 am EDT sun Sep 15 2019

- showers and a few storms especially this morning.

- Hazardous swim/boating conditions today.

- Warming trend this week.



&&

Discussion...(today through next saturday)
issued at 310 am EDT sun Sep 15 2019

An area of showers and thunderstorms will cross the County Warning Area this
morning. Radar shows them in WI and Illinois headed east. So many areas
will see rain this morning. The low level jet responsible for the
precipitation does pull east of the County Warning Area this morning...which
should result in a decreasing trend to the precipitation for the
afternoon. Still...recent guidance does show an axis of
instability hanging back over the County Warning Area for the afternoon. The
surface wave will still be west of the area as of 18z this
afternoon. So...there is some potential for showers to redevelop
this afternoon with a low risk for a storm or two...perhaps into
the evening. We did increase this risk for a storm accordingly.

Low level moisture persists through the night and even into
Monday. At the same time the surface wave and 850/700 mb trough
tracks through. We could see some showers/drizzle depending on how
the setup evolves. Some pops were added/increased to account for
this.

A mainly dry period will be forecasted into Thursday along with
moderating temperatures. At this time not much forcing will be
around to support precipitation as temperatures moderate. By
Friday though some instability is shown to advect in from the
west. There is some uncertainty as to whether this axis of
instability will arrive as much of the forcing remains well west
of the County Warning Area. We will hold off on featuring the risk for storms
until Saturday when most of the guidance suggests an eastward push
of the low level jet.




&&

Aviation...(for the 06z tafs through 06z Sunday night)
issued at 156 am EDT sun Sep 15 2019

We are watching shower/storm trends, and lower cloud trends for
the 06z set of forecasts. Models indicate that showers should
start forming by 09-10z over Lake Michigan, and that is indeed
starting to come true based on latest radar trends. It looks like
there will be scattered showers, that will eventually bring a
thunder chance as instability builds a little. The best chance for
thunder looks to occur after 08-09z, and lingers until 13z or so.

Some showers may linger, but the bigger item of interest looks to
be some lower clouds moving in. We are looking at a good chance of
MVFR cigs starting toward 18z, and lingering for much of the rest
of the forecast period. Cigs will start to go back to VFR around
and after 00z Mon.



&&

Marine...
issued at 310 am EDT sun Sep 15 2019

Winds were increasing ahead of the approaching wave of low
pressure. Waves were building as well. Not much change planned for
The Hazards as the scenario has not changed much. Some gusty winds
may accompany the storms over the waters. Much less wind is
expected for Monday as the pressure gradient weakens.




&&

GRR watches/warnings/advisories...
Michigan...Beach hazards statement from 8 am EDT this morning through this
afternoon for miz037-043-050-056-064-071.

Lm...Small Craft Advisory until 5 PM EDT this afternoon for
lmz844>849.

&&

$$

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